1. Field of the Invention
The present invention relates generally to location positioning. More particularly, the present invention relates to a method and an apparatus for efficiently controlling operation and power of a sensor in a positioning system that combines Global Navigation Satellite System (GNSS) or Global Positioning System (GPS) with an Inertial Navigation System (INS).
2. Description of the Related Art
In accordance with recent advances of mobile communication technologies, location positioning techniques have been developed to provide a new service based on locating a user. In general, the service using the location information is referred to as a Location Based Service (LBS).
Conventional location information acquisition methods typically include a method of location utilizing a Global Navigation Satellite System (GNSS), and/or a method of location that combines the GNSS and an Inertial Navigation System (INS).
The GNSS estimates the location based on a distance between a satellite and a receiver by measuring a time difference of received satellite signals. There is a problem in that the GNSS may not be able to measure the location because the signal is interrupted in a shadow zone (e.g., in buildings, under tall trees along the street, in a tunnel, and in the house). To avoid this, the INS operates based on the GNSS, particularly in those instances where the GNSS is unable to measure the location.
The INS estimates the relative location information by analyzing movement component and status information of a moving object using inertial sensors (e.g., accelerometer, gyroscope, and altimeter) and additional sensors (such as terrestrial magnetism sensor). Namely, the INS determines a location, a speed, and a direction of an object with respect to a known start point by measuring acceleration and angular velocity of the object and continually integrating them over time. Herein, the relative location information indicates a current location of the object measured by integrating the speed over time based on the start point.
The conventional system combining the GNSS and the INS enhances the overall location detection or expands the measurement range by adequately combining the relative location information from the GNSS and the location information from the INS.
However, even when the location information provided from the GNSS is accurate enough to offset the combination with the INS information, the system combining the GNSS and the INS continuously operates the INS, thus unnecessarily consuming power and degrading the overall system performance of the mobile device, such as a portable terminal.
For example, in an outdoor environment such as highway without a tall object, such as building or tree, around the user, the GPS location can be accurately demodulated because the GPS satellite signal is not subject to interference or multi-path. Accordingly, the GNSS alone can achieve the accurate location estimation in this situation. However, the positioning system combining the GNSS and the INS integrates the GNSS and the INS does not take into consideration such a situation.